Poly(L-glutamic) acid samples and other water-soluble polypeptides will be fractionated by glass pore chromatography to obtain a series of monodisperse fractions covering a broad range of molecular weights. Light scattering and viscometry will be employed to measure unperturbed molecular dimensions in the random-coil and the helix-coil transition regions as functions of milieu and of temperature. Comparison will be made of results with theory. Several double-alpha-helical proteins (tropomyosin, paramyosin, myosin tails) will be studied to examine the relationship of secondary to tertiary structure. The course of both thermal and guanidium chloride-induced denaturation will be followed both overall (backbone CD, light scattering) and at selected sites (Tyrosine CD). Formation and structural stability of various hybrid-helices will be studied, including inter-species hybrids (one clam chain, one worm chain) and inter-protein hybrids (one paramyosin chain, one myosin tail chain).